Unhandled panic when exporting variables

[lmorg]

Describe the bug:
Unhandled panic

Expected behaviour:
Not to crash

Screenshots:

.murex_modules » SSH_AUTH_SOCK=/var/folders/jc/z_166_bd26n6wtf3z9dbm_z40000gn/T//ssh-icbcGyY82Bee/agent.25341; export SSH_AUTH_SOCK;
Error in `SSH_AUTH_SOCK=/var/folders/jc/z_166_bd26n6wtf3z9dbm_z40000gn/T//ssh-icbcGyY82Bee/agent.25341` (0,1): fork/exec SSH_AUTH_SOCK=/var/folders/jc/z_166_bd26n6wtf3z9dbm_z40000gn/T//ssh-icbcGyY82Bee/agent.25341: no such file or directory
panic: runtime error: invalid memory address or nil pointer dereference
[signal SIGSEGV: segmentation violation code=0x2 addr=0x8 pc=0x102ce88c0]

goroutine 4964 [running]:
github.com/lmorg/murex/builtins/core/typemgmt.cmdExport(0x140004b9328)
        github.com/lmorg/murex/builtins/core/typemgmt/variables.go:128 +0x200
github.com/lmorg/murex/lang.executeProcess(0x140004b9328)
        github.com/lmorg/murex/lang/process.go:322 +0xeb8
created by github.com/lmorg/murex/lang.runModeNormal in goroutine 4928
        github.com/lmorg/murex/lang/interpreter_pc.go:49 +0x4c

Platform (please complete the following information):

• OS, output from uname -a if supported: macOS
• Terminal Emulator: iTerm2
• Murex version, output from version --no-app-name: 6.1.x

Additional context
None